Multi-speed transmission

ABSTRACT

A family of transmission gearing arrangements provides between eight and ten forward speed ratios and a reverse speed ratio. Three planetary gear sets are located on the input axis and a fourth planetary gear set is located on an offset axis. Axis transfer gears convey power between the input axis and the offset axis. One axis transfer gear is supported by a front support while another is supported by a center support. The center support also supports a clutch module and supplies pressurized fluid to engage the clutches in the clutch module.

TECHNICAL FIELD

This disclosure relates to the field of automatic transmissions formotor vehicles. More particularly, the disclosure pertains to anarrangement of gears, clutches, and the interconnections among them in apower transmission.

BACKGROUND

Many vehicles are used over a wide range of vehicle speeds, includingboth forward and reverse movement. Some types of engines, however, arecapable of operating efficiently only within a narrow range of speeds.Consequently, transmissions capable of efficiently transmitting power ata variety of speed ratios are frequently employed. When the vehicle isat low speed, the transmission is usually operated at a high speed ratiosuch that it multiplies the engine torque for improved acceleration. Athigh vehicle speed, operating the transmission at a low speed ratiopermits an engine speed associated with quiet, fuel efficient cruising.Typically, a transmission has a housing mounted to the vehiclestructure, an input driven by an engine crankshaft, often via a launchdevice such as a torque converter, and an output driving the vehiclewheels, often via a differential assembly which permits the left andright wheel to rotate at slightly different speeds as the vehicle turns.In front wheel drive vehicles with transverse mounted engines, theengine crankshaft axis is typically offset from the axle axis.

A common type of automatic transmission utilizes a collection ofclutches and brakes. Various subsets of the clutches and brakes areengaged to establish the various speed ratios. A common type of clutchutilizes a clutch pack having separator plates splined to a housing andinterleaved with friction plates splined to a rotating shell. When theseparator plates and the friction plates are forced together, torque maybe transmitted between the housing and the shell. Typically, a separatorplate on one end of the clutch pack, called a reaction plate, is axiallyheld to the housing. A piston applies axial force to a separator plateon the opposite end of the clutch pack, called a pressure plate,compressing the clutch pack. The piston force is generated by supplyingpressurized fluid to a chamber between the housing and the piston. For abrake, the housing may be integrated into the transmission case. For aclutch, the housing rotates. As the pressurized fluid flows from thestationary transmission case to the rotating housing, it may need tocross one or more interfaces between components rotating at differentspeeds. At each interface, seals direct the flow from an opening in onecomponent into an opening in the interfacing component.

SUMMARY OF THE DISCLOSURE

A transmission provides eight or ten speed ratios between an input shafton an input axis and an output shaft on an output axis. A first gearingarrangement on the input axis selectively imposes an overdriverelationship between a second shaft and a first shaft. The first gearingarrangement may be, for example, a simple planetary gear set with thesun gear fixedly coupled to the first shaft, the carrier fixedly coupledto the second shaft, and a first brake selectively holding the ring gearagainst rotation. A second gearing arrangement on the input axis fixedlyimposes a linear speed relationship among the first shaft, the inputshaft, and a third shaft. The second gearing arrangement may be, forexample, a simple planetary gear set with the sun gear fixedly coupledto the first shaft, the carrier fixedly coupled to the input shaft, andthe ring gear fixedly coupled to the third shaft. A third gearingarrangement on the output axis fixedly imposes a linear speedrelationship among a fifth shaft, the output shaft, and a sixth shaft.The second gearing arrangement may be, for example, a simple planetarygear set with the sun gear fixedly coupled to the sixth shaft, thecarrier fixedly coupled to the output shaft, and the ring gear fixedlycoupled to the fifth shaft. A fourth gearing arrangement fixedly imposesa proportional speed relationship between the second shaft and the fifthshaft. A fifth gearing arrangement fixedly imposes a proportional speedrelationship between a fourth shaft and the sixth shaft. The fourth andfifth gearing arrangements may each be, for example, pairs of axistransfer gears. As another example, the fourth and fifth gearingarrangements may each be two pairs of axis transfer gears in series. Thetransmission may also include a first brake selectively holding thefirst shaft against rotation, a first clutch selectively coupling theinput shaft to the fourth shaft, a second clutch selectively couplingthe second shaft to a seventh shaft, and a third clutch selectivelycoupling the third shaft to the seventh shaft.

In an eight speed embodiment, a sixth gearing arrangement fixedlyimposes a linear speed relationship among the third shaft, the seventhshaft, and the fourth shaft. The sixth gearing arrangement may be, forexample, a simple planetary gear set with the sun gear fixedly coupledto the third shaft, the carrier fixedly coupled to the seventh shaft,and the ring gear fixedly coupled to the fourth shaft. To save axialspace, the sixth gearing arrangement may be located radially outside thesecond gearing arrangement.

In a ten speed embodiment, a sixth gearing arrangement selectivelyimposes a linear speed relationship among the third shaft, the seventhshaft, and the fourth shaft. The sixth gearing arrangement may be, forexample, a simple planetary gear set with the sun gear fixedly coupledto the third shaft, the ring gear fixedly coupled to the fourth shaft,and the carrier selectively coupled to the seventh shaft by a fourthclutch. To save axial space, the sixth gearing arrangement may belocated radially outside the second gearing arrangement.

In some embodiments, the transmission has a front support and a centersupport each fixed to a transmission case. A first axis transfer gear issupported by the front support and a second axis transfer gear issupported by the center support on the side opposite the front support.A clutch module is also supported on the center support. In eight speedembodiments, the clutch module includes two clutches. In ten speedembodiments, the clutch module includes three clutches. The clutches areactuated by pressurized fluid routed through passageways in the centersupport into corresponding passageways in the clutch module.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a first transmission gearingarrangement.

FIG. 2 is a schematic diagram of a second transmission gearingarrangement.

FIG. 3 is a schematic diagram of a third transmission gearingarrangement.

FIG. 4 is a cross sectional view of a front support and clutch of atransmission according to the transmission arrangements of either FIG.1, FIG. 2, or FIG. 3.

FIG. 5 is a cross sectional view of a center support and clutch moduleof a transmission according to the transmission arrangements of eitherFIG. 1 or FIG. 2.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described herein. It is to beunderstood, however, that the disclosed embodiments are merely examplesand other embodiments can take various and alternative forms. Thefigures are not necessarily to scale; some features could be exaggeratedor minimized to show details of particular components. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a representative basis forteaching one skilled in the art to variously employ the presentinvention. As those of ordinary skill in the art will understand,various features illustrated and described with reference to any one ofthe figures can be combined with features illustrated in one or moreother figures to produce embodiments that are not explicitly illustratedor described. The combinations of features illustrated providerepresentative embodiments for typical applications. Variouscombinations and modifications of the features consistent with theteachings of this disclosure, however, could be desired for particularapplications or implementations.

A gearing arrangement is a collection of rotating elements and shiftelements configured to impose specified speed relationships among therotating elements. Some speed relationships, called fixed speedrelationships, are imposed regardless of the state of any shiftelements. Other speed relationships, called selective speedrelationships, are imposed only when particular shift elements are fullyengaged. A linear speed relationship exists among an ordered list ofrotating elements when i) the first and last rotating element in thegroup are constrained to have the most extreme speeds, ii) the speeds ofthe remaining rotating elements are each constrained to be a weightedaverage of the first and last rotating element, and iii) when the speedsof the rotating elements differ, they are constrained to be in thelisted order, either increasing or decreasing. The speed of an elementis positive when the element rotates in one direction and negative whenthe element rotates in the opposite direction. A proportional speedrelationship between two elements when the ratio between the speeds ofthe elements is a predetermined value. A proportional speed relationshipbetween a first element and a second element is an overdriverelationship if the second element always rotates faster than and in thesame direction as the first element. Similarly, a proportional speedrelationship between a first element and a second element is anunderdrive relationship if the second element always rotates slower thanand in the same direction as the first element.

A group of rotating elements are fixedly coupled to one another if theyare constrained to rotate as a unit in all operating conditions.Rotating elements can be fixedly coupled by spline connections, welding,press fitting, machining from a common solid, or other means. Slightvariations in rotational displacement between fixedly coupled elementscan occur such as displacement due to lash or shaft compliance. One ormore rotating elements that are all fixedly coupled to one another maybe called a shaft. In contrast, two rotating elements are selectivelycoupled by a shift element when the shift element constrains them torotate as a unit whenever it is fully engaged and they are free torotate at distinct speeds in at least some other operating condition. Ashift element that holds a rotating element against rotation byselectively connecting it to the housing is called a brake. A shiftelement that selectively couples two or more rotating elements to oneanother is called a clutch. Shift elements may be actively controlleddevices such as hydraulically or electrically actuated clutches orbrakes or may be passive devices such as one way clutches or brakes. Tworotating elements are coupled if they are either fixedly coupled orselectively coupled.

An element is a transmission input if it is adapted to be fixedlycoupled to either a power source or the output of a launch device. Apower source may be, for example, an internal combustion engine or anelectric motor. A launch device may be, for example, a torque converteror a launch clutch. The input may be coupled to the power source orlaunch device via a damper designed to absorb torsional vibrations. Anelement is a transmission output if it is adapted to transmit power tocomponents outside the transmission such as vehicle wheels. There may bea fixed speed ratio other than 1:1 between the output element and thedriven component.

An example transmission is schematically illustrated in FIG. 1. In thistransmission, input 10 is driven by the engine, preferably via a launchdevice such as a torque converter or launch clutch. Output gear 12rotates about a second axis that is parallel to and offset from theinput axis. An additional gear, not shown, transmits power from theoutput gear to the differential which is located on a third axis.

The transmission of FIG. 1 utilizes four simple planetary gear sets 20,30, 40, and 50. A simple planetary gear set is a type of fixed gearingarrangement. A planet carrier 22 rotates about a central axis andsupports a set of planet gears 24 such that the planet gears rotate withrespect to the planet carrier. External gear teeth on the planet gearsmesh with external gear teeth on a sun gear 26 and with internal gearteeth on a ring gear 28. The sun gear and ring gear are supported torotate about the same axis as the carrier. A simple planetary gear setimposes a fixed speed relationship. The speed of the carrier isconstrained to be between the speed of the sun gear and the speed of thering gear. More specifically, the speed of the carrier is a weightedaverage of the speed of the sun gear and the speed of the ring gear withweighting factors determined by the number of teeth on each gear.Similar speed relationships are imposed by other known types of fixedgearing arrangements. For example, a double pinion planetary gear setconstrains the speed of the ring gear to be a weighted average betweenthe speed of the sun gear and the speed of the carrier. Gear sets 30,40, and 50 are similarly structured.

The transmission also utilizes four axis transfer gears 78, 80, 82, and84. A pair of meshing axis transfer gears forms another type of fixedgearing arrangement. Axis transfer gear 78 is supported to rotate abouta first axis while axis transfer gear 80 is supported to rotate aboutsecond axis parallel to and offset from the first axis. External gearteeth on the gear 78 mesh with external gear teeth on a gear 80. A pairof meshing axis transfer gears imposes a proportional speedrelationship. The gears rotate in opposite directions at speeds relatedby the ratio of the number of teeth on each gear. Proportional speedrelationships are imposed by other known types of fixed gearingarrangements. For example, a chain and sprocket arrangement imposes aproportional speed relationship between the sprockets. As anotherexample, a planetary gear set with one element held against rotationimposes a proportional speed relationship between the remaining twoelements.

A suggested ratio of gear teeth for each planetary gear set is listed inTable 1.

TABLE 1 Ring 28/Sun 26 2.20 Ring 38/Sun 36 1.75 Ring 48/Sun 46 1.60 Ring58/Sun 56 3.70 Gear 80/Gear 78 1.00 Gear 84/Gear 82 1.00

Sun gear 26 is fixedly coupled to sun gear 36 forming a first shaft.Carrier 22 is fixedly couple to axis transfer gear 82 forming a secondshaft. Ring gear 38 is fixedly coupled to sun gear 46 forming a thirdshaft. Ring gear 48 is fixedly coupled to axis transfer gear 78 forminga fourth shaft. Input shaft 10 is fixedly coupled to carrier 32. Ringgear 58 is fixedly coupled to axis transfer gear 84 forming a fifthshaft. Sun gear 56 is fixedly coupled to axis transfer gear 80 forming asixth shaft. Finally, output shaft 12 is fixedly coupled to carrier 52.

Ring gear 28 is selectively held against rotation by brake 66 and thefirst shaft (sun gears 26 and 36) is selectively held against rotationby brake 68. Input shaft 10 is selectively coupled to the fourth shaft(ring gear 48 and axis transfer gear 78) by clutch 70. Intermediateshaft 64 is selectively coupled to carrier 42 by clutch 72, selectivelycoupled to the second shaft (carrier 22 and axis transfer gear 82) byclutch 74, and selectively coupled to the third shaft (ring gear 38 andsun gear 46) by clutch 76.

Various combinations of gearing and shift elements impose particularspeed relationships among the shafts. Planetary gear set 20 and brake 66selectively impose an overdrive relationship between the second shaftand the first shaft. In other words, when brake 66 is engaged, sun gear26 rotates faster than carrier 22 and in the same direction. Gear set 30fixedly imposes a linear speed relationship between the first shaft, theinput shaft, and the third shaft. Similarly, gear set 50 fixedly imposesa linear speed relationship between the fifth shaft, the output shaft,and the sixth shaft. Axis transfer gears 82 and 84 fixedly impose aproportional speed relationship between the second and the fifth shafts.Similarly, axis transfer gears 78 and 80 fixedly impose a proportionalspeed relationship between the fourth shaft and the sixth shaft.

As shown in Table 2, engaging the shift elements in combinations of fourestablishes ten forward speed ratios and one reverse speed ratio betweeninput shaft 10 and output shaft 12. An X indicates that the shiftelement is required to establish the speed ratio. An (X) indicates theshift element can be applied but is not required. In 1^(st) gear, eitherclutch 74 or clutch 76 can be applied instead of applying clutch 72without changing the speed ratio. When the gear sets have tooth numbersas indicated in Table 1, the speed ratios have the values indicated inTable 2.

TABLE 2 66 68 70 72 74 76 Ratio Step Rev X X X X −4.79 102% 1^(st) X X X(X) 4.70 2^(nd) X X X X 2.99 1.57 3^(rd) X X X X 2.18 1.37 4^(th) X X XX 1.80 1.21 5^(th) X X X X 1.54 1.17 6^(th) X X X X 1.29 1.19 7^(th) X XX X 1.00 1.29 8^(th) X X X X 0.85 1.17 9^(th) X X X X 0.69 1.24 10^(th) X X X X 0.64 1.08

Another example transmission is illustrated in FIG. 2. In thistransmission, output shaft 12 and planetary gear set 50 are located onthe same axis as the differential. Axis transfer gears 86, 88, 90, and92 all rotate about an intermediate axis parallel to and offset fromboth the input shaft axis and the output shaft axis. Axis transfer gears86, 88, 90, and 92 are in continuous meshing engagement with axistransfer gears 78, 80, 82, and 84 respectively. Gear 86 is fixedlycoupled to gear 88. Gear 90 is fixedly coupled to gear 92.Alternatively, gears 90 and 92 could rotate about a different axis thangears 86 and 88. Axis transfer gears 82, 90, 92, and 84 fixedly impose aproportional speed relationship between the second and the fifth shafts.Similarly, axis transfer gears 78, 86, 88, and 80 fixedly impose aproportional speed relationship between the fourth shaft and the sixthshaft.

A third example transmission is illustrated in FIG. 3. In thistransmission, clutch 72 has been replaced with a fixed connectionbetween intermediate shaft 64 and carrier 42. As shown in Table 3,engaging the shift elements in combinations of three establishes eightforward speed ratios and one reverse speed ratio between input shaft 10and output shaft 12. When the gear sets have tooth numbers as indicatedin Table 1, the speed ratios have the values indicated in Table 3.

TABLE 3 66 68 70 74 76 Ratio Step Rev X X X −4.79 102% 1^(st) X X X 4.702^(nd) X X X 2.99 1.57 3^(rd) X X X 2.18 1.37 4^(th) X X X 1.80 1.215^(th) X X X 1.29 1.40 6^(th) X X X 1.00 1.29 7^(th) X X X 0.85 1.178^(th) X X X 0.64 1.32

FIG. 4 is a cross sectional view of a front support, clutch 70, and axistransfer gear 78. Front support 102 is fixed to transmission case 14between the gearbox and the launch device. Housing 104 is supported forrotation about the front support by bearings 106 and 108. Input shaft 10is supported for rotation by bearing 110. Axis transfer gear 78 is fixedto housing 102. Shell 112 connects housing 102 to ring gear 48. Theseparator plates of clutch pack 70 are splined to shell 112 andinterleaved with friction plates splined to hub 114 which is fixed toinput shaft 10. Piston 116 is supported within housing 104 between sealsto form clutch apply chamber 118.

A series of passageways 120 formed into front support 104 route fluidfrom a valve body to various destinations. Seals separate the fluidpassageways as they pass between the stationary front support and therotating input shaft 10 or housing 102. Some passageways route fluidinto input shaft 10 to control a torque converter. One passageway routesfluid into clutch apply chamber 118. When fluid within clutch applychamber 118 is pressurized, piston 116 slides axially and forces theseparator plates and friction plates of clutch pack 70 together.Frictional forces between the separator plates and friction platestransmit torque between the input shaft 10 and housing 104. When thepressure in clutch apply chamber 118 is reduced, return spring 122forces the piston to slide away from clutch pack 70. Centrifugal forcescan pressurize fluid within clutch apply chamber 118, which if notcompensated, could cause unintended clutch application. To compensate,another passageway routed unpressurized fluid into balance chamber 124.

FIG. 5 is a cross sectional view of a center support, clutch module,gear set 20, and axis transfer gear 82. Center support 132 is fixed totransmission case 14. Carrier 22 is supported for rotation about thecenter support by bearing 134. Axis transfer gear 82 is fixed to carrier22. Clutch housing 136 is supported for rotation about center support132 on the opposite side from carrier 22 by bearings 170 and 172. Hollowshaft 138 extends through center support 132 connecting carrier 22 toclutch hub 140. Hollow shaft 138 is supported by center support 132 bybearing 174. Shaft 142 extends through hollow shaft 138 and connects sungear 26 to sun gear 36. Shaft 142 is supported by bearing 176. Clutchhub 144 is fixed to ring gear 38 and sun gear 46. Clutch hub 146 isfixed to carrier 42.

A network of passageways 148 in center support 132 carries fluid fromthe valve body. A network of passageways 150 in clutch housing 136routes fluid to various chambers to engage clutches 72, 74, and 76.Fluid passes between center support 132 and clutch housing 136 betweenseals such that each passageway in the center support is fluidlyconnected to a particular passageway in clutch housing 136. Onepassageway provides fluid to clutch apply chamber 152, forcing piston154 to engage clutch 74. Another passageway provides fluid to clutchapply chamber 156, forcing piston 158 to engage clutch 76. A thirdpassageway provides fluid to clutch apply chamber 160, forcing piston162 to engage clutch 72. Finally, a fourth passageway providesunpressurized fluid to balance chambers 164, 166, and 168 to preventunintended clutch application due to centrifugal force.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms encompassed by the claims.The words used in the specification are words of description rather thanlimitation, and it is understood that various changes can be madewithout departing from the spirit and scope of the disclosure. Aspreviously described, the features of various embodiments can becombined to form further embodiments of the invention that may not beexplicitly described or illustrated. While various embodiments couldhave been described as providing advantages or being preferred overother embodiments or prior art implementations with respect to one ormore desired characteristics, those of ordinary skill in the artrecognize that one or more features or characteristics can becompromised to achieve desired overall system attributes, which dependon the specific application and implementation. These attributes caninclude, but are not limited to cost, strength, durability, life cyclecost, marketability, appearance, packaging, size, serviceability,weight, manufacturability, ease of assembly, etc. As such, embodimentsdescribed as less desirable than other embodiments or prior artimplementations with respect to one or more characteristics are notoutside the scope of the disclosure and can be desirable for particularapplications.

1. A transmission comprising: an input shaft configured to rotate aboutan input axis; an output shaft configured to rotate about an output axisoffset from the input axis; first, second, third, and fourth shaftsconfigured to rotate about the input axis; fifth and sixth shaftsconfigured to rotate about the output axis; a first gearing arrangementconfigured to selectively impose an overdrive relationship between thesecond shaft and the first shaft; a second gearing arrangementconfigured to fixedly impose a linear speed relationship among the firstshaft, the input shaft, and the third shaft; a third gearing arrangementconfigured to fixedly impose a linear speed relationship among the fifthshaft, the output shaft, and the sixth shaft; a fourth gearingarrangement configured to fixedly impose a proportional speedrelationship between the second shaft and the fifth shaft; and a fifthgearing arrangement configured to fixedly impose a proportional speedrelationship between the fourth shaft and the sixth shaft.
 2. Thetransmission of claim 1 wherein the first gearing arrangement comprises:a first sun gear fixedly coupled to the first shaft; a first ring gear;a first carrier fixedly coupled to the second shaft; a first set ofplanet gears supported for rotation relative to the first carrier and incontinuous meshing engagement with the first sun gear and the first ringgear; and a first brake configured to selectively hold the first ringgear against rotation.
 3. The transmission of claim 1 wherein the secondgearing arrangement comprises: a second sun gear fixedly coupled to thefirst shaft; a second ring gear fixedly coupled to the third shaft; asecond carrier fixedly coupled to the input shaft; and a second set ofplanet gears supported for rotation relative to the second carrier andin continuous meshing engagement with the second sun gear and the secondring gear.
 4. The transmission of claim 1 wherein the third gearingarrangement comprises: a third sun gear fixedly coupled to the sixthshaft; a third ring gear fixedly coupled to the fifth shaft; a thirdcarrier fixedly coupled to the output shaft; and a third set of planetgears supported for rotation relative to the third carrier and incontinuous meshing engagement with the third sun gear and the third ringgear.
 5. The transmission of claim 1 wherein the fourth gearingarrangement comprises: a first axis transfer gear fixedly coupled to thesecond shaft; and a second axis transfer gear fixedly coupled to thefifth shaft and in continuous meshing engagement with the first axistransfer gear.
 6. The transmission of claim 1 wherein the fifth gearingarrangement comprises: a third axis transfer gear fixedly coupled to thefourth shaft; and a fourth axis transfer gear fixedly coupled to thesixth shaft and in continuous meshing engagement with the third axistransfer gear.
 7. The transmission of claim 1 wherein the fourth gearingarrangement comprises: a first axis transfer gear fixedly coupled to thesecond shaft; a fifth axis transfer gear configured to rotate about anintermediate axis and in continuous meshing engagement with the firstaxis transfer gear; a sixth axis transfer gear fixedly coupled to thefifth axis transfer gear; and a second axis transfer gear fixedlycoupled to the fifth shaft and in continuous meshing engagement with thesixth axis transfer gear.
 8. The transmission of claim 1 wherein thefifth gearing arrangement comprises: a third axis transfer gear fixedlycoupled to the fourth shaft; and a seventh axis transfer gear configuredto rotate about an intermediate axis and in continuous meshingengagement with the third axis transfer gear; an eighth axis transfergear fixedly coupled to the seventh axis transfer gear; and a fourthaxis transfer gear fixedly coupled to the sixth shaft and in continuousmeshing engagement with the eighth axis transfer gear.
 9. Thetransmission of claim 1 further comprising: a seventh shaft configuredto rotate about the input axis; a second brake configured to selectivelyhold the first shaft against rotation; a first clutch configured toselectively couple the input shaft to the fourth shaft; a second clutchconfigured to selectively couple the second shaft to the seventh shaft;and a third clutch configured to selectively couple the third shaft tothe seventh shaft.
 10. The transmission of claim 9 further comprising: asixth gearing arrangement configured to fixedly impose a linear speedrelationship among the third shaft, the seventh shaft, and the fourthshaft.
 11. The transmission of claim 10 wherein the sixth gearingarrangement comprises: a fourth sun gear fixedly coupled to the thirdshaft; a fourth ring gear fixedly coupled to the fourth shaft; a fourthcarrier fixedly coupled to the seventh shaft; and a fourth set of planetgears supported for rotation relative to the fourth carrier and incontinuous meshing engagement with the fourth sun gear and the fourthring gear.
 12. The transmission of claim 9 wherein the third clutch isconfigured to selectively couple the third shaft directly to the seventhshaft.
 13. The transmission of claim 9 wherein the sixth gearingarrangement is located radially outside the second gearing arrangement.14. The transmission of claim 9 further comprising: a sixth gearingarrangement configured to selectively impose a linear speed relationshipamong the third shaft, the seventh shaft, and the fourth shaft.
 15. Thetransmission of claim 14 wherein the sixth gearing arrangementcomprises: a fourth sun gear fixedly coupled to the third shaft; afourth ring gear fixedly coupled to the fourth shaft; a fourth carrier;a fourth set of planet gears supported for rotation relative to thefourth carrier and in continuous meshing engagement with the fourth sungear and the fourth ring gear; and a fourth clutch configured toselectively couple the seventh shaft to the fourth carrier.
 16. Thetransmission of claim 14 wherein the sixth gearing arrangement islocated radially outside the second gearing arrangement.
 17. Atransmission comprising: a transmission case; a center support fixedlycoupled to the transmission case; a first axis transfer gear supportedby the center support and located on a first side of the center support;and a clutch module having three clutches supported by the centersupport and located on a second side of the center support.
 18. Thetransmission of claim 17 further comprising: a front support fixedlycoupled to the transmission case and located on the second side of thecenter support; and a second axis transfer gear supported by the frontsupport.
 19. The transmission of claim 18 further comprising: a firstset of separator plates splined to the second axis transfer gear; afirst set of friction plates interleaved with the first sets ofseparator plates; and a first piston configured to slide axially withina first chamber in the second axis transfer gear.
 20. The transmissionof claim 17 wherein the clutch module comprises: a clutch housingdefining second, third, and fourth chambers and further defining fluidpassageways between each of the second, third, and fourth chambers andan inner surface; and second, third, and fourth pistons configured toslide axially within the second, third, and fourth chambers respectivelyin response to pressurization of fluid in the respective passageway. 21.The transmission of claim 20 wherein the center support defines fluidpassageways between the transmission case and a surface of the centersupport adjacent to the inner surface of the clutch housing.
 22. Atransmission comprising: a transmission case; a front support fixedlycoupled to the transmission case; a first axis transfer gear supportedby the front support; a center support fixedly coupled to thetransmission case; a clutch module supported by the center support andlocated between the front support and the center support; and a secondaxis transfer gear supported by the center support.
 23. The transmissionof claim 22 wherein the clutch module comprises: a housing; a firstclutch pack having a plurality of separator plates splined to thehousing and a friction plate splined to a first hub wherein the firsthub is fixedly coupled to the second axis transfer gear; and a firstpiston configured to slide axially with respect to the housing, thefirst piston and the housing defining a first apply chamber.
 24. Thetransmission of claim 23 wherein the clutch module further comprises: asecond clutch pack having a plurality of separator plates splined to thehousing and a friction plate splined to a second hub; and a secondpiston configured to slide axially with respect to the housing, thesecond piston and the housing defining a second apply chamber.
 25. Thetransmission of claim 24 wherein: the housing defines a first passagewaybetween the first apply chamber and an inner surface of the housing; thehousing defines a second passageway between the second apply chamber andthe inner surface of the housing; and the center support defines aplurality of fluid passageways configured to convey fluid from thetransmission case to the first and second passageways in the housing.26. The transmission of claim 25 further comprising: an input; anoutput; a first planetary gear set having a first sun gear, a first ringgear, a first carrier fixedly coupled to the second axis transfer gear,and a plurality of planet gears supported for rotation with respect tothe first carrier and meshing with both the first sun gear and the firstring gear; a second planetary gear set having a second sun gear fixedlycoupled to the first sun gear, a second ring gear fixedly coupled to thesecond hub, a second carrier fixedly coupled to the input, and aplurality of planet gears supported for rotation with respect to thesecond carrier and meshing with both the second sun gear and the secondring gear; a third planetary gear set having a third sun gear fixedlycoupled to the second ring gear, a third ring gear fixedly coupled tothe first axis transfer gear, a third carrier coupled to housing, and aplurality of planet gears supported for rotation with respect to thethird carrier and meshing with both the third sun gear and the thirdring gear; a fourth planetary gear set having a fourth sun gear fixedlyconstrained to have a proportional speed relationship with the firstaxis transfer gear, a fourth ring gear fixedly constrained to have aproportional speed relationship with the second axis transfer gear, afourth carrier fixedly coupled to the output, and a plurality of planetgears supported for rotation with respect to the fourth carrier andmeshing with both the fourth sun gear and the fourth ring gear; a firstbrake configured to selectively couple the first sun gear to thetransmission case; a second brake configured to selectively couple thefirst ring gear to the transmission case; and a fourth clutch configuredto selectively couple the first axis transfer gear to the input.
 27. Thetransmission of claim 24 wherein the clutch module further comprises: athird clutch pack having a plurality of separator plates splined to thehousing and a friction plate splined to a third hub; and a third pistonconfigured to slide axially with respect to the housing, the thirdpiston and the housing defining a third apply chamber.
 28. Thetransmission of claim 27 wherein: the housing defines a first passagewaybetween the first apply chamber and an inner surface of the housing; thehousing defines a second passageway between the second apply chamber andthe inner surface of the housing; the housing defines a third passagewaybetween the third apply chamber and the inner surface of the housing;and the center support defines a plurality of fluid passagewaysconfigured to convey fluid from the transmission case to the first,second, and third passageways in the housing.
 29. The transmission ofclaim 28 further comprising: an input; an output; a first planetary gearset having a first sun gear, a first ring gear, a first carrier fixedlycoupled to the second axis transfer gear, and a plurality of planetgears supported for rotation with respect to the first carrier andmeshing with both the first sun gear and the first ring gear; a secondplanetary gear set having a second sun gear fixedly coupled to the firstsun gear, a second ring gear fixedly coupled to the second hub, a secondcarrier fixedly coupled to the input, and a plurality of planet gearssupported for rotation with respect to the second carrier and meshingwith both the second sun gear and the second ring gear; a thirdplanetary gear set having a third sun gear fixedly coupled to the secondring gear, a third ring gear fixedly coupled to the first axis transfergear, a third carrier fixedly coupled to the third hub, and a pluralityof planet gears supported for rotation with respect to the third carrierand meshing with both the third sun gear and the third ring gear; afourth planetary gear set having a fourth sun gear fixedly constrainedto have a proportional speed relationship with the first axis transfergear, a fourth ring gear fixedly constrained to have a proportionalspeed relationship with the second axis transfer gear, a fourth carrierfixedly coupled to the output, and a plurality of planet gears supportedfor rotation with respect to the fourth carrier and meshing with boththe fourth sun gear and the fourth ring gear; a first brake configuredto selectively couple the first sun gear to the transmission case; asecond brake configured to selectively couple the first ring gear to thetransmission case; and a fourth clutch configured to selectively couplethe first axis transfer gear to the input.